20 
SALOON. 
Nat. Hist. 
stances, viz. specimens of the noble opal , which 
owes its beautiful play of colours to a multiplicity 
of imperceptible fissures in its interior ; the Mexi¬ 
can sun or fire opal 5 the common opal , a translu¬ 
cent white variety of which, appearing yellow or 
red when held between the eye and the light, is 
called girasol; the semi-opal , agreeing in its prin¬ 
cipal characters with the common ; specimens of 
those varieties which, having the property of be¬ 
coming transparent when immersed in water, are 
called hydrophanes, and vulgarly oculus mundi ; 
wood-opal , or opalised wood ; jasp-opal , referred 
by some authors to jasper; the menilite , called 
also liver-opal, found at Menil-Montant, near 
Paris, in a bed of adhesive slate, a specimen of 
which is added. Some varieties of cacholong 
may likewise be referred to the opal tribe.—The 
remainder of this case is occupied by the siliceous 
substance called hornstone , divided into the con- 
choidal and splintery varieties ; among these are 
the remarkable pseudomorphous crystals from 
Schneeberg in Saxony, derived from various 
modifications of calcareous spar, and generally 
referred to conchoidal hornstone; also some 
beautiful specimens of wood converted into horn¬ 
stone, being the wood-stone of Werner ; horn¬ 
stone balls, from Plaunstadt in Bavaria.— Flinty 
slate , &c. 
Case 9. In this case are deposited (besides 
the specimens of rock crystals continued from 
the opposite compartment of the table-case) the 
different 
